Ladder device



April 2, 1963 o. HERTERICH ETAL LADDER DEVICE 5 Sheets-Sheet 1 FiledNOV. 8, 1960 INVENTORS 6W t April 1963 o. HERTERICH ET AL 3,083,789

LADDER DEVICE Filed Nov. 8, 1960 3 Sheets-Sheet 2 /N VE N TOPS MM HM ABY April 2, 1963 o. HERTERICH ET AL 3,083,789

LADDER DEVICE Filed Nov. 8, 1960 3 Sheets-Sheet 3 INVENZOR5 WM UnitedStates Patent 3,333,789 LADDER DEVEQE Qslrar Herterich and ErichHuttner, Uhn (Danube), Germany, assignors to Kinelrner-HumholdhfieutzA.G.,

Kola, Germany Filed Nov. 8, 1960, Ser. No. 67,995 Qlaiins priority,application Germany Nov. 11, 1959 8 Claims. (til. 182-212) The presentinvention relates to ladders.

More particularly, the present invention relates to extension ladders ofthe type used, for example, in fire fighting.

Conventional extension ladders of this type maintain the several laddersections at select d elevations with respect to each other by means ofhooks carried by the lower one of a pair of adjacent ladder sections andextending around a selected rung of the upper one of the pair ofsections, which is to say that section which extends upwardly beyond butstill overlaps the next lower section. While such hooks reliably holdthe several ladder sections at the desired elevations, nevertheless theysuffer from a serious disadvantage. Thus, with these conventionalstructures in order to collapse the extension ladder it is necessaryfirst to expand the latter beyond the position in which it happens to beso as to separate the books from the rungs and enable the hooks to beturned to positions where they will not interfere with the downwardmovement of all except the lowermost ladder section. Thus, whenever afireman, for example, wishes to collapse the extension ladder it isfirst necessary to move all except the lowermost ladder section upwardlyto a more extended position through a distance approximately equal toone-half the distance between a pair of successive ladder rungs, andonly after this initial extending of the ladder can it be collapsed. Asa result of this requirement of first further extending the ladderbefore it can be collapsed, considerable skill is required to operatethe extension ladder and only the most skilled firerne can operateextension ladders rapidly and efficient y.

It is therefore a primary object of the present invention to provide anextension ladder which can be moved from an extended to a collapsedposition without first requiring the ladder to be extended beyond theextended position it happens to be in before it is desired to collapsethe ladder.

Another object of the present invention is to provide a structure whichwill operate effectively with any extension ladder irrespective of thenumber of ladder sections of th extension ladder.

An additional object of the present invention is to provide an extensionladder which will reliably prevent any ladder sections from fallingfreely before their weight is carried by the rope used for raising andlowering the ladder section.

It is also an object of the present invention to provide a simple andeiiicient hydraulic control for an extension ladder of the above type.

With the above objects in view the present invention includes, in anextension ladder, a first ladder section which extends in a generallyupward direction and remains stationary during use of the extensionladder, and a second ladder section which overlaps and is longitudinallymovable with respect to the stationary ladder section upwardly to anextended position and downwardly to a collapsed position. A pawl meansengages a rung of the movable ladder section to maintain the latter inits extended position, and this pawl means is movable from an en agedposition engag ng a rung of the movable ladder action to a disengagedposition spaced from the rungs of the movable ladder section and locatedon the same side of the rungs of the movable ladder section as thestationary ladder section. This pawl means of the present invention isacted upon by a moving means of the present invention which moves thepawl means in a generally downward direction from its engaged toward itsdisengaged position so that at this time the pawl means moves in thesame general direction that the movable ladder section moves when movingfrom its extended toward its collapsed position, and therefore with thestructure of the invention it becomes unnecessary to raise the movableladder section before it can be lowered to its collapsed position.

The novel features which are considered as characteristic for theinvention are set forth in particular in the appended claims. Theinvention itself, however, both as to its construction and its method ofoperation, together with additional objects and advantages thereof, willbe best understood from the following description of specificembodiments when read in connection with the accompanying drawings, inwhich:

HS. 1 is a side elevation illustrating diagrammatically the manner inwhich the structure of the invention cooperates with a pair of laddersections;

FIG. 2 shows the structure of FIG. 1 in a position different from FIG.1;

FIG. 3 shows the structure of FIGS. 1 and 2 in a third positiondifferent from the positions of H63. 1 and 2;

. FIG. 4 is a partly diagrammatic illustration of still anotherembodiment of the present invention;

FlG. 5 shows the structure of FIG. 4 in a position different from thatof FIG. 4; and

P16. 6 schematically illustrates an extension ladder according to thepresent invention and the hydraulic control means therefor.

Referring to FlGS. 1-3, a stationary ladder section 1 forms the lower ofthe pair of ladder sections 11 and 2 shown fragmentarily in PEG. 1.Although the ladder section 1 is referred to as being stationary in thisdescrip tion and in the claims which follow, it is to be understood thatthe stationary ladder section is stationary in the sense that it remainsstationary during use of the extension ladder and forms the lowermostsection of the extension ladder. The stationary ladder section 1 iscapable of being turned from a horizontal position on a fire truckupwardly to a position where the stationary ladder section extends in agenerally upward direction during use of the extension ladder. Thestationary ladder section ll carries, in a manner described below inconnection with H6. 6, ropes 3 guided over suitable pulleys carried bythe stationary ladder section 1 and connected with pins or the likewhich are fixed to the movable ladder section 2 so that this movableladder section is carried by the ropes 3 and is capable of being movedup and down by way of the ropes 3. The movable ladder section 2 overlapsthe stationary ladder section l and is movable upwardly with respectthereto to an extended position and downwardly with respect thereto to acollapsed position.

The structure of the invention includes a pawl means which in theembodiment of FIGS. 1-3 is formed by the pawl member 4. A moving meanscooperates with this pawl means for moving it from the position of FIG.1 to that of FIG. 3. The pawl means 4 is shown in an engaged position inFIG. 1, and it will be seen that when the pawl means 4 is in its engagedposition it engages the underside of a rung 8 of the movable laddersection 2 for preventing downward movement of the movable laddersection. On the other hand, in the disengaged position of the pawl means4- which is shown in FIG. 3 this pawl means has been displaced out ofthe plane in which the rungs of the movable ladder section are locatedtoward the plane in which the rungs of the stationary ladder Section arelocated, so that when the pawl means 4- is in the disengaged positionshown in FIG. 3 the ropes 3 can be actuated to lower the movable laddersection to its collapsed position.

In accordance with the present invention the moving means which movesthe pawl means 4 moves the latter from its engaged position first in agenerally downward direction and then in a direction toward the plane inwhich the rungs of the stationary ladder section are located. Thus,during the initial movement of the pawl means 4 from its engaged towardits disengaged position the pawl means moves in the same generaldirection that the movable ladder section moves when moving downwardlyfrom its extended toward its collapsed position, and thus it isunnecessary with the present invention to raise the movable laddersection before it can be lowered to its collapsed position.

The moving means of the invention, according to the embodiment of FIGS.1-3, includes the lever to one end of which the pawl 4 is pivoted.Actually the free end portion of the lever 5 which carries the pawl 4 isbifurcated to receive a portion of the pawl 4, and as is apparent fromFIGS. 1 and 2 which show in a dotted line the innermost part of thebifurcation, the innermost part of the bifurcation limits the turningmovement of the pawl 4 in a clockwise direction by the spring 12, sothat the pawl 4 cannot move in a clockwise direction, as viewed in FIGS.land 2, beyond the position shown'in FIGS. 1 and 2. However, the pawl 4is free to turn in opposition to the spring 12 in a counter clockwisedirection, as viewed in FIGS. 1 and 2.

The moving means which moves the pawl 4' is carried by the stationaryladder section I and includes a support means which supports the lever 5for turning movement at its end portion distant from the pawl 4. Thislever 5 is supported for turning movement in a generally downwarddirection from the position of FIG. 1 to that of FIG. 3 for moving thepawl means 4 from its engaged position shown in FIG. 1 to its disengagedposition shown in FIG. 3, and of course the lever 5' is supported by thesupport means for turning movement in a generally upward direction fromthe position of FIG. 3 to that of FIG. 1 for placing the pawl means 4 inits engaged position.

The moving means includes in addition to the lever 5 a hydraulic controlmeans which controls the movement of the lever 5, and this hydrauliccontrol means includes a second lever 6 which is turnable between theposition shown in FIGS. 1 and 2 and the position shown in FIG. 3. In theposition of FIGS. 1 and 2 the lever 6 maintains the lever 5 in its upperposition and the pawl 4 in its engaged position, and it will be notedthat at this time the lever 6 extends perpendicularly with respect tothe lever 5 so that there is no tendency for the lever 6 to turn and itis subject only to pure compression. The hydraulic means includes, inaddition to the lever 6 which is supported by the support means carriedby the stationary ladder section 1 for turning movement about an axisparallel to the turning axis of the lever 5, a hydrauliccylinder-and-piston means 7. The cylinder of the cylinder-and-pistonmeans 7 is stationary and is supplied at its bottom end through aconduit 13 with a fluid under pressure. The piston of thecylinder-and-piston means 7 is urged by a spring downwardly to theposition shown in FIG. 2, so that the spring of the cylinder-and-pist-onmeans seeks to maintain the lever 6 in a position extendingperpendicularly to the lever 5 and thus the spring of thecylinder-and-piston means tends to locate the parts in the positionshown in FIGS. 1 and 2. The hydraulic fluid which enters through theconduit 13 into the cylinder-and-piston means 7 raises the pistonthereof in opposition to the spring in the cylinder so as to turn thelever 6 to the position shown in FIG. 3. At this time the piston willhave uncovered a return flow conduit 14'so that the piston is shown inFIG. 3 in one of its end positions. During the counter clockwise turningof the lever 6 from the position of FIG. 2 to that of FIG. 3 the lever 5is turned by its own weight downwardly from the position of FIG. 2 tothat of FIG. 3 so as to place the pawl means 4 in its collapsedposition.

After the ladder has been fully collapsed, and it will be noted that inthe position of FIG. 3 the pawl 4 does not interfere with the rungs ofthe movable section 2 so that the latter can be quickly collapsed, thefluid under pressure is no longer supplied through the conduit 13 andthe spring acts on the piston of the cylinder-and-piston means 7 'forreturning the parts 46 to the position shown in FIGS. 1 and 2. When itis desired to extend the ladder, the movable section 2 is simply movedupwardly, and it will be noted that the several rungs 8 as they pass thepawl 4 will simply turn the latter in opposition to the spring 12 aseach rung 8 engages and moves beyond the pawl 4, as is apparent fromFIG. 2. Once the movable ladder section has been moved up to the desiredelevation it is simply allowed to descend through whatever distance isrequired to place the lung 8 which is located directly over the pawl 4in engagement with the upper end thereof, as indicated in FIG. 1, andthe ladder will now remain in its extended position.

In the embodiment of the invention which is illustrated in FIGS. 4 and 5the pawl means is formed by the elongated pawl member 19 which has afree end adapted to engage a rung 8 of the movable ladder section 2 inthe manner illustrated in FIG. 4, when the pawl means is in its engagedposition, so as to maintain the movable ladder section in its extendedposition.

The moving means which moves the pawl means 19 is again carried by thestationary ladder section 1 and also includes a lever. Thus, as is shownin FIG. 4, a lever 18 is provided, and this lever 18 pivotally carriesat its right free end portion, as viewed in FIGS. 4 and 5, the pawlmeans 19. The cylinder of the cylinder-and-piston means 7 is fixedlycarried by the stationary ladder section 1, and this cylinder has anintegral rigid extension which pivotally carries the lever 18.

In the embodiment of FIGS. 4 and 5 the lever 18 has, in addition to itsarm which carries the pawl means 19, a second arm extending beyond thepivotal support for the part of the lever carrying the pawl means 19,and this second arm is pivotally connected to the piston of thecylinder-and-piston means 7. The spring of this cylinderand-piston meansmaintains the parts in the position shown in FIG. 4, and in thisposition the ropes 3 can at any time be acted upon to raise the movableladder section 2 from its collapsed position and the rungs 8 willsuccessively ride past pawl 19, and a selected rung 8 can then be placedin engagement with the pawl in the manner shown in FIG. 4.

It will be noted that the pawl 19 is fixed with an elongated member 20which forms a bell crank with the pawl 19, and a supporting structurefor the cylinder-and-piston means 7 carries a stationary member 21 whichforms a stop to limit the turning of the extension 20' in a clockwisedirection, as viewed in FIGS. 4 and 5. A spring is connected at one endto the framework and at its opposite end to the extension 20 to urge thelatter together with the pawl 19 in a clockwise direction, as viewed inFIGS. 4 and 5. Thus, as the rungs 8 move upwardly past pawl 19, the pawl19 together with the extension 20 will be free to turn in a counterclockwise direction in opposition to the spring and will thenimmediately return to the position determined by the stop 21 as soon asa rung 8 has moved upwardly beyond the pawl "19.

It will be noted that when a rung 8 is engaged by the I pawl 19 in theposition shown in FIG. 4, the movable that when the parts are in theposition shown in FIG. 4 there is virtually no stress on the piston ofthe cylinderand piston means 7. Of course, when it is desired to movethe pawl means 19 to its disengaged position shown in FIG. 5 fluid underpressure is introduced through the conduit 13 into the cylinder of thecylinder-and-piston means 7 so as to advance the piston toward theconduit 14 and eventually the piston will reach the position shown inFIG. 5, the piston at this time moving in opposition to the springwithin the cylinder of the cylinder-and-piston means 7. During theinitial clockwise turning of the lever id, as viewed in FIG. 4, the endof the pawl 19 pivotally connected to the lever 18 will move downwardly,and of course at this time the extension 20 will slide along the stopmember 2-1, the result being that during the initial portion of theturning of the lever 18 from the position of FIG. 4 to that of FIG. 5the pawl 19 moves downwardly while remaining in engagement with the rung3 so that the ropes 3 which may be slack when the parts have theposition shown in FIG. 4 Will be tensioned and will take up the weightof the ladder section 2. After the initial portion of the movement ofthe lever 18, which may constitute approximately the first half of itstotal stroke, for example, the continued turning of the lever 18together with the maintenance of the extension 20 against the stop 21will result in turning of the pawl 19 away from the plane in which therungs of the ladder section 2 are located toward the plane in which therungs of the stationary ladder section 1 are located. Of course, as soonas the pawl 19 is out of the plane in which the rungs 8 are located theladder section 2 can be lowered to its collapsed position.

With the embodiment of FIGS. 1-3 as well as with the embodiment of FIGS.4 and 5 the lever which is connected to the pawl means turns so as tomove the pawl means first in a generally downward direction in advanceof the downward movement of the ladder section 2 so that the ropes 3will be fully tensioned by the weight of the ladder section 2 before thepawl means leaves the movable ladder section, and thus, free falling ofthe movable ladder section with sudden yanking of the ropes 3 isreliably avoided.

FIG. 6 illustrates diagrammatically the hydraulic installation as wellas the several sections of a ladder and the cable system for actuatingthe sections. Thus, it will be seen from FIG. 6 that the stationaryladder section 1 forms the lowest of the ladder sections while themovable ladder section 2 is the next highest ladder section, and a pairof additional successive ladder sections are shown in FIG. 6. The ropes3 which support the movable ladder section 2 are guided over pulleyscarried by upper portions of the stationary ladder section '1, and theseropes 3 are connected with a winch 25 which can be turned in onedirection or the other so as to take up or let out the ropes 3 and thusraise or lower the movable ladder section 2.

As may be seen from FIG. 6, a pair of additional ropes are respectivelyfixed to the top ends of the side members of the stationary laddersection 1, are guided over pulleys carried by upper side portions of theladder section 2, and me connected with lower side portions of the thirdladder section. As a result when the movable ladder section 2 movesupwardly, the pulleys carried thereby also move upwardly and act on theropes guided over these pulleys to raise the third ladder sectionsimultaneously with the raising of the second ladder section 2, and ofcourse the third ladder section will by its own weight descend when theladder section 2 descends.

In much the same way a third set of ropes 3 are fixed to the top ends ofthe ladder section 2, are guided over pulleys carried by the thirdladder section and are connected to bottom end portions of the fourthladder section, so that as the third ladder section moves up and downthe pulleys carried thereby will also move up and down to act on thethird set of cables for raising and lowering the fourth ladder section,and thus it is apparent that operation of the winch 25 will result inraising and lowering of the entire extension ladder irrespective of thenumber of sections included in the extension ladder. Furthermore it isapparent that the single pawl means carried by the moving meanssupported by the stationary ladder section 1 and cooperating with asingle rung of the movable ladder section 2 will act to maintain theentire extension ladder extended to the degree selected by the operator.

As is apparent from FIG. 6, there are actually a pair of pawlscooperating with the selected rung of the movable ladder section, andFIG. 6 shows the pair of levers 6 of the embodiment of FIGS. 13. Thepair of levers 6 are supported by a common pivot pin in the form of anelongated rod, and in the same way the pair of levers 5 which cooperatewith the pair of levers 6 may also be supported by a common rod passingtherethrough. The pair or" pawls 4 which form the pawl means may beinterconnected by a rod which will guarantee that they turn as a unit.In the same way a pair or pawls l9 and extensions 26 as well as a pairof levers 18 are provided for the embodiment of FIGS. 4 and 5. However,only one cylinder-and-piston means is provided, as indicated in FIG. 6.

The winch 25 is driven by an oil motor 26 which acts through thereduction gearing assembly 27 on the winch 25. Oil under pressure isdelivered to the motor 26 to actuate the latter from a pump 23 whichderives the oil from a reservoir 29. The oil after passing through themotor 2% returns by way of a conduit 31 back to the tank 29. The flow ofoil is controlled by a manually operable valve means 32 which isillustrated in FIG. 6 in its neutral position. The diagrammaticallyillustrated valve means 32 has a handle 35 accessible to the operatorfor manipulating the valve. When the handle 35 is turned in a clockwisedirection, as viewed in FIG. 6, from the illustrated neutral positionthe ladder will be collapsed, While when the handle 35 is turned in acounter clockwise direction, as viewed in FIG. 6, from the illustratedneutral position the ladder will be extended. The turnable valve memberof the valve means 32 includes a bore 33 passing diametricallytherethrough, a relatively small bore il extending perpendicularly fromthe bore 33, an arcuate groove 37, and a substantially sickleshapedgroove 38 communicating with the end of the bore 41 distant from thebore 33. The discharge conduit 36 for the fluid under pressure deliveredby the pump 23 leads from the pump 23 to the valve means 32, andupstream of the valve means 32 is a safety valve which providescommunication between the conduits 30 and 36 in the event that thepressure in the conduit 36 becomes too high. The pressure conduit 13leads from the cylinder-and-piston means '7 to the valve 32, while theconduit 114 communicates directly with the return flow conduit 38. Aconduit 34 provides communication between the valve 32 and the returnflow conduit 3d, and a conduit 4% leads from the valve 32 to the motor26. It will be noted that the conduits 13, 35, ll} and 34 respectivelycommunicate with the valve 32 at points angularly spaced by with respectto each other.

Assuming that the ladder is collapsed and that it is desired to extendthe ladder, the operator will simply turn the handle 35' in a counterclockwise direction through a relatively small angle suihcient to placeconduits 36 and id in communication with each other through the groove33. At this time the opposite ends of the bore 33 will be closed, andthe conduits l3 and 34- will be placed in communication with each otherso that the conduit 13 at this time is at low pressure and thus thespring of the cylinder-and-piston means will have no difiiculty inmaintaining the pawl means 4 or 19 in its engaged position. The handle35 is held in the position where the conduits 36 and 40 communicatethrough the groove 3i; until the desired degree of extension of the seaves ladder is obtained, and then the handle 35 is returned by theoperator to the neutral position shown in FIG. '6. At this time thegroove 37 does not communicate with the conduit 34 so that the conduit13 is closed, and thus the piston of the cylinder-and-piston means 7 isvery reliably held in its lowermost position shown in FIGS. 1 and 4because the force required to raise the piston would have to besuflicient to produce a vacuum in the hollow interior of conduit 13 andgroove 37 which is filled with oil. Thus, the pawl means is veryreliably held in its extended position and the rung of the laddersection 2 which engages the pawl means is very reliably supported. Itmay be that when the operator returns the valve 32 to its neutralposition the selected rung of the ladder section 2 is spaced above thepawl means. As is apparent from FIG. 6 when the valve 32 is in its neutral position the bore 33 provides communication between the conduits 36and 34 so that the fluid under pressure simply circulates back to thereservoir 29. Also, in the neutral position of the valve 32 the pressureconduit 40 of the motor 26 communicates through the groove 38 and thebore 41 of relatively small diameter with the bore 33 and conduit 34. Asa result the weight of the movable ladder sections will cause them tomove downwardly turning the winch 25 and the gearing 27 as well as themotor 26 through which the fluid can now flow in the reverse directionthrough the conduit 40 and slowly through the bore 41 back along theconduits 34 and 30 to the reservoir, so that in this Way irrespective ofthe height of the selected rung of the ladder section 2 above the pawlmeans when the operator returns the lever 35 to its neutral position,the ladder will automatically move down until the selected rung rests onand is supported:

by the pawl means.

When it is desired to collapse the extended ladder, the operator turnsthe handle 35 in a clockwise direction through an angle as sufficient toplace conduits l3 and 36 in communication with each other through thegroove 37 and conduits 34 and 40 in communication with each otherthrough the groove 38. In this way the motor 26 will easily turn in thedirection reverse to the winding direction since the conduit 40communicates with the return flow conduit without the resistance to theflow provided by the conduit 41 of small diameter. Thus, the movableladder sections will be able to descend fairly rapidly under their ownweight, the resistance provided by the flow of the hydraulic fluidthrough the conduit 40 and the conduit 34 preventing free falling of theladder sections. Of course, the downward movement of the ladder sectionswill not start until the piston is displaced in the cylinder of thecylinder-and-piston means 7 and the fluid under pressure flowing throughthe conduit 13 displaces the piston so as to initiate the collapse ofthe ladder in the manner described above. Once the pawl means has movedout of the plane of the rungs '8, the ladder sections move downwardlyand the motor 26 simply turns in a reverse direction, the fluid at thistime simply circulating around through the motor through theshort-circuit provided by the communication between the conduits 40 and34. Of course, when the piston has been displaced beyond the conduit 14the fluid under pressure will return through the conduit 14 to the tank29. Once the conduit 14 receives fluid from the conduit 13, part of thefluid from the conduit 14 may flow to the motor 26 to replace fluiddisplaced therefrom into the conduit 40, and the ladder sections willdescend in the manner described above. As soon as the ladder is totallycollapsed the operator returns the valve 32 to its neutral position.

The provision of a pair of ropes 3 for each of the movable laddersections located beyond the ladder section 2 provides the desired safetysince if any one rope should fail the other rope will still hold theladder section. 7

Also, the pawl means may of course be made up 3 of a single pawl memberrather than a pair of interconnected pawl members.

It will be understood that each of the elements described above, or twoor more together, may also find a useful application in other types ofladders diifering from the types described above.

While the invention has been illustrated and described as embodied inextension ladders, it is not intended to be limited to the detailsshown, since various modifications and structural changes may be madewithout departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist ofthe present invention that others can by applying current knowledgereadily adapt it for various applications without omitting featuresthat, from the standpoint of prior art, fairly constitute essentialcharacteristics of the generic and specific aspects of this inventionand, therefore, such adaptations should and are intended to becomprehended within the meaning and range of equivalence of thefollowing claims.

What is claimed as new and desired to be secured by Letters Patent is:

1. In an extension ladder, in combination, a first ladder sectionadapted to remain stationary while extending in a generally upwarddirection during use of the extension ladder; a second ladder sectionoverlapping said first ladder section and movable longitudinally withrespect thereto in a generally upward direction to an extended positionand in a generally downward direction to a collapsed position; pawlmeans pivotable about a pivot axis therethrough and having an engagedposition engaging a rung of said movable ladder section for preventingdownward movement thereof and a disengaged position spaced from andlocated on the same side of the rungs of said movable ladder section assaid stationary ladder section, said pivot axis in said disengagedposition of said pawl means being located downwardly from its locationin the engaged position of said pawl means; a lever pivotally connectedto said pawl means at said pivot axis; support means carried by saidstationary ladder section and supporting said lever for turning movementin a downward direction for moving said pawl means firom said engagedposition to said disengaged position and in an upward direction formoving said pawl means from said disengaged to said engaged positionthereof; and means cooperating with said lever for controlling theturning movement thereof.

2. In an extension ladder, in combination, a first ladder sect-ionadapted to remain stationary while extending in a gene-rally upwarddirection during use of the extension ladder; a second ladder sectionoverlapping said first ladder section and movable longitudinally withrespect thereto in a generally upward direction to an extended positionand in a generally downward direction to a collapsed position; pawlmeans pivotable about a pivot axis therethrough and having an engagedposition engaging a rung of said movable ladder section for preventingdownward movement thereof and a disengaged position spaced from andlocated on the same side of the rungs of said movable ladder section assaid stationary ladder section, said pivot axis in said disengagedposition of said pawl means being located downwardly from its locationin the engaged position of said pawl means; a lever pivot-ally connectedto said pawl means at said pivot axis; support means carried by saidstationary ladder section and supporting said lever for turning movementin a downward direction for moving said pawl mean-s from said engagedposition to said disengaged position and in an upward direction formoving said pawl means from said disengaged to said engaged positionthereof; and hydraulic means cooperating with said lever for controllingthe turn ing movement thereof, said hydraulic means controlling saidlever so that the latter will move downwardly in advance of the downwardmovement of said movable ladder section toward said collapsed positionthereof.

3. In an extension ladder, in combination, a first ladder spear s9section adapted to remain stationary while extending in a generallyupward direction during use of the extension ladder; a second laddersection overlapping said first ladder section and movable longitudinallywith respect thereto in a generally upward direction to an extendedposition and in a generally downward direction to a collapsed position;pawl means pivotable about a pivot axis thercthrough and having anengaged position engaging a rung of said movable ladder section forpreventing downward movement thereof and a disengaged position spacedfrom and located on the same side of the rungs of said movable laddersection as said stationary ladder section, said pivot axis in saiddisengaged position of said pawl means being located downwardly from itslocation in the engaged position of said pawl means; a lever pivotallyconnected to said pawl means at said pivot axis; support means carriedby said stationary ladder section and supporting said lever for turningmovement in a downward direction for moving said pawl means from saidengaged position to said disengaged position and in an upward directionfor moving said pawl means from said disengaged to said engaged positionthereof; and hydraulic means cooperating with said lever for controllingthe turning movement thereof, said lever during its downward turningmovement moving said pawl means first in a generally downward directionand then away from the plane in which the rungs of said movable laddersection are located toward the plane in which the rungs of saidstationary ladder section are located.

4. in an extension ladder, in combination, a first ladder sectionadapted to remain stationary while extending in a generally upwarddirection during use of the extension ladder; a second ladder sectionoverlapping said first ladder section and movable longitudinally withrespect thereto in a generally upward direction to an extended positionand in a generally downward direction to a collapsed position; pawlmeans having an engaged position engaging a rung of said movable laddersection for preventing downward movement thereof and a disengagedposition spaced from and located on the same side of the rungs of saidmovable ladder section as said stationary ladder section; a leverpivotally carrying said pawl means at one end portion of said lever;support means carried by said stationary ladder section and supportingsaid lever at an opposite end portion thereof for turning movement in agenerally downward and generally upward direction, said lever whenturning in said generally downward direction moving said pawl meanstoward said disengaged position thereof to release said movable laddersection for movement to said collapsed position thereof without firstrequiring raising of said movable ladder section; a second leverturnably carried by said support means and extending substantiallyperpendicularly with respect to and engaging said first-mentioned leverat an underside thereof for preventing downward movement of saidfirst-mentioned lever when said pawl means is in said engaged positionthereof; and hydraulic means operatively connected with said secondlever for turning the latter to a position where said second leverextends at an acute angle with respect to said first-men tioned leverand releases the latter for downward movewent so as to move said pawlmeans from said engaged toward said disengaged position thereof.

5. In an extension ladder, in combination, a first ladder sectionadapted to remain stationary while extending in a generally upwarddirection during use of the extension ladder; a second ladder sectionoverlapping said first ladder section and movable longitudinally withrespect thereto in a generally upward direction to an extended positionand in a generally downward direction to a collapsed position; pawlmeans having an engaged position engaging a rung of said movable laddersection for preventing downward movement thereof and a disengagedposition spaced from and located on the same side of the rungs of saidmovable ladder section as said stationary ladder section; a leverpivotally carrying said pawl means at one end portion of said lever;support means carried by said stationary ladder section and supportingsaid lever at an opposite end portion thereof for turning movement in agenerally downward and generally upward direction, said lever whenturning in said generally downward direction moving said pawl meanstoward said disengaged position thereof .to release said movable laddersection for movement to said collapsed position thereof without firstrequiring raising of said movable ladder section; a second leverturnably carried by said support means and extending substantiallyperpendicularly with respect to and engaging said first-mentioned leverat an underside thereof for preventing downward movement of saidfirst-mentioned lever when said pawl means is in said engaged positionthereof; and hydraulic means operatively connected with said secondlever for turning the latter to a position where said second leverextends at an acute angle with respect to said first-mentioned lever andreleases the latter for downward movement so as to move said pawl meansfrom said engaged toward said disengaged position thereof, said secondlever having at one end a freely turnabie roller engaging saidfirst-mentioned lever.

6. In an extension ladder, in combination, a first ladder sectionadapted to remain stationary while extending in a generally upwarddirection during use of the extension ladder; a second ladder sectionoverlapping said first ladder section and movable longitudinally withrespect thereto in a generally upward direction to an extended positionand in a generally downward direction to a collapsed position; pawlmeans pivotable about a pivot axis therethrough and having an engagedposition engaging a rung of said movable ladder section for preventingdownward movement thereof and a disengaged position spaced from andlocated on the same side of the rungs of said movable ladder section assaid stationary ladder section, said pivot axis in said disengagedposition of said pawl means being located downwardly from its locationin the engaged position or" said pawl means; a lever pivotally connectedto said pawl means at one end portion of said lever and at said pivotaxis; support means carried by said stationary ladder section andsupporting said lever for turning movement in generally upward anddownward directions for moving said pawl means between said engaged anddisengaged positions thereof, respectively, said pawl means including anelongated member which engages a rung of said movable ladder sectionwhen said pawl means is in said engaged position thereof and saidelongated member extending in the same direction as and formingsubstantially an extension of said lever when said pawl means is in saidengaged position thereof; and means cooperating with said lever forcontrolling the turning movement thereof.

7. In an extension ladder, in combination, a first ladder sectionadapted to remain stationary while extending in a generally upwarddirection during use of the extension ladder; a second ladder sectionoverlapping said first ladder section and movable longitudinally withrespect thereto in a generally upward direction to an extended positionand in a generally downward direction to a collapsed position; pawlmeans pivotable about an axis therethrough and having an engagedposition engaging a rung of said movable ladder section for preventingdownward movement thereof and a disengaged position spaced from andlocated on the same side of the rungs of said movable ladder section assaid stationary ladder section, said pivot axis in said disengagedposition of said pawl means being located downwardly from its locationin the engaged position of said pawl means; a lever pivotally connectedto said pawl means at one end portion of said lever and at said pivotaxis; support means carried by said stationary ladder section andsupporting said lever for turning movement in generally upward andspar-agree downward directions for moving said pawl means between saidengaged and disengaged positions thereof, respectively, said pawl meansincluding an elongated member which engages a rung of said movableladder section when said pawl means is in said engaged position thereofand said elongated member extending in the same direction as and formingsubstantially an extension of said lever when said pawl means is in saidengaged position thereof, said lever having an extension extendingbeyond the turning axis provided by said support means and forming anarm of said lever; and hydraulic means operatively connected with saidarm for turning said lever so as to move said pawl means between saidpositions thereof.

8. In an extension ladder, in combination, a first ladder sectionadapted to remain stationary while extending in a generally upwarddirection during use of the extension ladder; a second ladder sectionoverlapping said first ladder section and movable longitudinally withrespect thereto in a generally upward direction to an extended positionand in a generally downward direction to a collapsed position; pawlmeans pivotable about a pivot axis therethrough and having an engagedposition engaging a rung of said movable ladder section for preventingdownward movement thereof and a disengaged position spaced from andlocated on the same side of the rungs of said movable ladder section assaid stationary ladder section, said pivot axis in said disengagedposition of said pawl means being located downwardly from its locationin the engaged position of said pawl means; a lever pivotally connectedto said pawl means at one end portion of said lever and at said pivotaxis; support means carried by said stationary ladder section andsupporting said lever for turning movement in generally upward anddownward directions folmoving said pawl means between said engaged anddisengaged positions thereof, respectively, said pawl means including anelongated member which engages a rung of said movable ladder sectionwhen said pawl means is in said engaged position thereof and saidelongated member extending in the same direction as and formingsubstantially an extension of said lever when said pawl means is in saidengaged position thereof, said pawl means including a second elongatedmember fixed to and extending angularly from said firstmentionedelongated member and said stationary ladder section carrying a stopmember in the path of movement of said second elongated member duringdownward turning of said lever while said pawl means moves from saidengaged toward said disengaged position for engaging said secondelongated member and turning said pawl means with respect to said leverwhile the latter continues its downward movement for displacing saidpawl means out of the plane in which the rungs of said movable laddersection are located toward the plane in which the rungs of saidstationary ladder section are located; and means cooperating with saidlever for controlling the turning movement thereof.

References Cited in the file of this patent UNITED STATES PATENTS786,687 Sekcwsky Apr. 4, 1905 983,212 Dahil-l Jan. 31, 1911 1,277,504Tanner Sept. 3, 1918 1,394,263 Adell Oct. 18, 1921 1,746,475 House Feb.11, 1930 2,318,567 Duerig May 4, 1943 2,853,221 Troche Sept. 23, 19582,896,750 Eitel July 2 8, 1959 2,932,486 Suderow Apr. '12, 1960

1. IN AN EXTENSION LADDER, IN COMBINATION, A FIRST LADDER SECTIONADAPTED TO REMAIN STATIONARY WHILE EXTENDING IN A GENERALLY UPWARDDIRECTION DURING USE OF THE EXTENSION LADDER; A SECOND LADDER SECTIONOVERLAPPING SAID FIRST LADDER SECTION AND MOVABLE LONGITUDINALLY WITHRESPECT THERETO IN A GENERALLY UPWARD DIRECTION TO AN EXTENDED POSITIONAND IN A GENERALLY DOWNWARD DIRECTION TO A COLLAPSED POSITION; PAWLMEANS PIVOTABLE ABOUT A PIVOT AXIS THERETHROUGH AND HAVING AN ENGAGEDPOSITION ENGAGING A RUNG OF SAID MOVABLE LADDER SECTION FOR PREVENTINGDOWNWARD MOVEMENT THEREOF AND A DISENGAGED POSITION SPACED FROM ANDLOCATED ON THE SAME SIDE OF THE RUNGS OF SAID MOVABLE LADDER SECTION ASSAID STATIONARY LADDER SECTION, SAID PIVOT AXIS IN SAID DISENGAGEDPOSITION OF SAID PAWL MEANS BEING LOCATED DOWNWARDLY FROM ITS LOCATIONIN THE ENGAGED POSITION OF SAID PAWL MEANS; A LEVER PIVOTALLY CONNECTEDTO SAID PAWL MEANS AT SAID PIVOT AXIS; SUPPORT MEANS CARRIED BY SAIDSTATIONARY LADDER SECTION AND SUPPORTING SAID LEVER FOR TURNING MOVEMENTIN A DOWNWARD DIRECTION FOR MOVING SAID PAWL MEANS FROM SAID ENGAGEDPOSITION TO SAID DISENGAGED POSITION AND IN AN UPWARD DIRECTION FORMOVING SAID PAWL MEANS FROM SAID DISENGAGED TO SAID ENGAGED POSITIONTHEREOF; AND MEANS COOPERATING WITH SAID LEVER FOR CONTROLLING THETURNING MOVEMENT THEREOF.